In order to assure adequate skiing in most areas of the world over an extended ski season, many such areas cannot fully rely upon natural snow to provide an adequate snow cover for such purpose. Consequently, apparatus and methods for making artificial snow are required both in the United States and in other countries to insure a profitable skiing season for many, if not most, operators of ski areas.
At the present time, two principal systems for making artificial snow are in use. The first such system, often referred to as an "air" system, utilizes a relatively large air compressor which is located at a centralized position (e.g. at the bottom of one or more ski slopes) and which provides compressed air fed through appropriate pipes to one or more remote locations of the ski area. Water under pressure is also supplied to such remote locations from a central water source which may, for example, be located near the air compressor. The compressed air and pressurized water are fed to appropriate "snow guns" which merely mix the two components in various ways to provide artificial snow. Such systems are relatively expensive to install and operate. The compressors must be quite large if they are to provide a sufficient supply of compressed air at more than a few locations.
In such air systems, the air flow rates at each gun may vary depending on the size of the guns that are being used, such air flow rates ranging from as low as about 100 cubic feet per minute (c.f.m.) to as high as 1,800-2,000 c.f.m., for example. Even at the relatively high end of the range of air flow rates, relatively little water is converted into snow despite the relatively large amount of air that is compressed for such purpose. Moreover, such installations are very costly to install and to operate. A known system, for example, which utilizes two relatively large air compressors, supplying a total combined output of 6,000 c.f.m. of compressed air to only three remotely located snow guns, can provide relatively little snow even at these few locations at any one time. The installation costs of such a system may well run as high as $200,000.00 or more, which represents a large investment with less return than is desirable to make the use thereof economically justifiable.
One advantage of using such conventional compressed air systems however, is that their operation can produce artificial snow at relatively high ambient temperatures i.e., at temperatures, which while below sub-freezing, are generally about or above 26.degree. F, as compared with other "airless" artificial snow making systems discussed below which usually require temperatures lower than about 26.degree. F for providing adequate snow-making performance. Accordingly, such compressed air systems are generally found necessary for use in ski areas where the average mean temperature even in the cold months is generally higher than 26.degree. F.
Another system which has been utilized in many ski areas is often referred to as an "airless" system wherein a plurality of snow-making units located at a plurality of remote locations of a ski area each use either internal combustion motors or electric motors to drive air propellers associated therewith to produce a cold air stream at each snow-making unit. Water from a centralized source is piped under pressure to each of such locations and suitable snow guns provide an appropriate mixture of the water with a cold air stream created by the propellers to produce artificial snow. While the system tends to provide for conversion of larger amounts of water to snow than the "air" systems as described above and eliminates the high cost of installing a relatively large central air compressor, each of the individual air propeller and motor units at the remote locations are in themselves relatively expensive. Moreover, appropriate electrical power, for example, must be supplied to each unit when electrical motors are used, requiring the laying of a large number of cables over the ski area. Such systems are considered relatively dangerous where high voltage industrial electric sources must be used, particularly at night under adverse conditions. Moreover, the relatively large size and overall weight of such motor units makes them cumbersome to move from one remote location to another as well as making it difficult to position them in a stable manner on relatively steep slopes. A further and significant disadvantage of such systems, which do not use compressed air is that they are not as effective at temperatures at or above about 26.degree. F as are conventional "air" systems which are presently available.